Electric cable



May 24, 193s. C. www@ M3263@ ELECTRIC CABLE Filed, l5, 19358 (APS)INVENTOR Buhl,

`COMM/Groff.; 60A/9mm? M445 Z5/WHW @5M/SNT @amg/V7* AT1 ORNLLYS PatentedMay 24, 1938 PATENT OFFICE ELECTRIC CABLE Richard C. WaldromClifton, N.J., assignor to The Okonite Company, Passaic, N. J., a corporation ofNew Jersey Application January 15, 1936, Serial No'. 59,204

4 Claims.

This invention relates to an improvement in electric cables particularlyadapted for vertical suspension as for example in the exploration of oilwells, and has for one of its objects the provision of a cable which isso constructed as to limit or restrict the elongation of the cableconductors. In previous cables for vertical suspension diillculty isexperienced with elongation of the conductor of the cable to such anextent that upon contraction of the cable, i. e., restoration of thecable to its original length, the conductor buckles, repetition causingthe conductor to break. This difficulty is eliminated in the presentconstruction.

One of the objects of the present invention is the provision of anelectric cable construction in which stretching of the conductor is socontrolled that the cable can be elongated and restored to its originallength without buckling and breaking of the conductor, my copendingapplication Serial No. 58,475, tiled January l0, 1936, showing aconstruction inwhich the conductor will stretch and contract with thecable without deformation.

More specifically the present invention'provides a cable construction inwhich the conductor is applied helically about an extensible,incompressible core at a critical lay, the lay of the conductor aboutthe core being such that upon initial elongation of the cable theconductor is elongated to a predetermined degree, elongation of theconductor being so controlled and restricted by the core and the lay ofthe conductor about the core that upon the tension being removed fromthe cable the 'cable can be restored to its original length withoutbuckling of the conductor.

Comparing the cable of my invention with prior cables, and assuming thesame certain desired percentage elongation of the cable in bothinstances, in prior cable structures the conductor is stretched to suchan extent that upon return of the cable to its original length theconductor buckles, repetition resulting in breaking of the conductor;with my improved cable the conductor is so laid up about the core thatthe stretch or elongation of the conductor is materially reduced, and asa consequence, although the percentage of elongation of the cable is thesame in both instances, my cable can be elongated and contractedrepeatedly without buckling and breaking of the conductor. l

In addition to all of the foregoing in my improved construction the layof the conductor is sufiiciently long so that the cable cannot bestretched without the conductors pulling down on the core and beingdeformed. As a consequence my construction adds the iullstrength of theconductor to the core due to the conductor pulling down on the core. Itwill be appreciated that this is of advantage in manufacture and avoidsbreakage of the core in manufacturing the cable.

Referring to the drawing: Fig. i is a part sectional View of a bodyingmy invention; l

Fig. 2 is a cross section of the cable of Fig. l; Figs. 3 and 4 arecross sectional views illustrating the relative positions of the cableconductor and core at different stages of elongation of the cable;

Fig. 5 shows one strand of the unstretched cable conductor about a coreof extensible sub cable emstantially incompressible material ;V

Fig. 5A is an end view of thestructure of Fig. 5;

Fig. 5B is a development of a cylinder Whose O diameter is the pitchdiameter of the strand of Fig. 5 and whose length is the length of layof the strand of Fig. 5;

Fig. 6 shows the core and strand of Fig. 5 in stretched position;

Fig. 6A is an end view of Fig. 6;

Fig. 6B is a development of a cylinder whose diameter is the pitchdiameter of the stretched strand of Fig. 6 and Whose length is thelength of lay of the strand of Fig. 6; 30

Fig. 7 shows the condition ofthe conductor strand after the strand andcore of Fig. 5 have been elongated and then allowed to contract;

Fig. '7A is an end view of Fig. r1;

Fig. 7B is a development of a cylinder whose diameter is the pitchdiameter of the strand of Fig. 7 and whose length is the length of layof the strand of Fig. 7;

Fig. 8 shows one type of conductor which may` be employed in thepractice of my'invention;

Fig. 9 shows another type of conductor; and Fig. 10 still another type;

Figs. 11 and 12 are views of modified embodiments of my inventionwherein multi-conductor cables are shown instead of the single conductor45 cable of Fig. 1.

Referring to the drawing in detail and first of all to the constructionillustrated in Figs. 1 to 7B, inclusive. I designates the core of myimproved cable. This core is of pliable, exten- 50 sible, substantiallyincompressible material such as rubber. A brous material may be employedfor the core if desired, such as silk or cotton thread, for example,which may be twisted together so as to provide a core which issufliciently 55 incompressible and yet at the same time s cientlyextensible and pliable for iny purpose.

About tlrls extensible, substantially incon sible core apply theconductor il. This conductorniay be composed of copper strandsliellcally applied in parallel relation with a predetermined lay abouttbe core l as will be brought ont in detail hereinafter. Directly overthe conductor 2 'i apply insulation 3. This may be the usual rubber orrubber compound insulation commonly employed in electric cable Work.

About insulation 3 l apply a fabric cover-- ing l which may be in theform of a fabric tane saturated with oil and moisture impervious inamterial such as .rvel which is an acid condensa- 'tion product made fromthe oil obtained from cashew nnt shells.

designates a supporting armor consisting o-rnv stranded steel `wires.These wires are the as commonly employed in steel wire rope and' may belaid up in any of the methods common to wire robe manufacture.

.as cointed ont at the outset of tliis desert on, one oi the objects ofmy invention is the provision oi an electric cable wherein aconstruction is provided by which detrimental stretching of theconductor is avoided, tbe present construction providing that theelongation o the cable conductor shall be limited to apoint or degreewhere tbe cable a `whole may elongate and contract tvltbont detrimentalbuckling and eventual brealring oi the cono `,ctor. This construction isnrovided Under the present invention by applying the conductor theextensible, incompressible core oi the ca 1le with predetermined lay,which li term the c cal" lay. li the angle of lay of the conductor aboutthe core is too long then npon elongation of the cable the insidediameter of the helix provided by the conductor decreases too fast ascompared with the decrease in the outside diameter of tbe core andupondesiredelon gation oi the cable the conductor will be excessivelystretched. On the other hand, the. lay is too short then the outsidediameter of the core decreases too tast as compared with the decrease`in the inside diameter of the helix provided by the conductor and theconductor adds no strength to the core. ln accordance with the lpresentinvention the conductor is laici about the core at such an angle thatinitially were the cable compressed, i. e. shortened, the core wouldincrease in diameter faster than the conductor, and on elongation of thecable the conductor tends to pull down on the core.

With reference to the showing in Figs. 5 through 7B of the drawing,Figs. 5 and 5a show the initial position of each conductor strand.

da=the diameter of the core l d :the diameter of each strand of thecable condnctor D:pitch diameter of each strand or the con'- ductor:da-Hi L :length of lay of each strand of the conduc- In Fig. 6 I haveillustrated the core and strand of Fig. 5 in stretched position. Heredo:the diameter of the core l under the assumed conditions Di :the pitchdiameter of the conductor strands a' :length or conductor strand for onecomplete about the core l i :'sercentage elongation which the cable isdesigned decimal) e l the cable has l een elongated and then allowed tocontract and here f""n:t" diameter of tbe core 6:62@ lli :tne T oitclodiameta the conductor strand The lay of the condnctor il enen thatinitially, as .chown ir about and in contact 'w n the cable is allowed te. 7, to origi cl le' dnctor i, however, o conductor has bee conductor-will again decrease outside diameter o'4 the core l niaiiininn elongatiof the reached conductor :vill agaii l but Without further stretching oitne c toi'. ieese conditions exist only tor a @erin critical lay", ofthe conductor the formula that vv `1 cable ln tbis oi cable theconductor ma" terially to the tensile strength or" the core will beappreciated inasmuch as the permitted elongation of the conductor isless 'than possible elongation of the core before breaking. is anadvantage in manufacture in that it gives additional strength to thecore.

As above mentioned an object of my invention Upon stretching theconductor the strand length c is increased as can be shown by ananalysis oi the equation Dol=dol+d ol: do 41+ IFT #1,015+ d) Upon returnof the conductor to its normal length after this initial stretch we havewhich is obviously larger than D. The increase in D depends on theincrease in a or on the stretch 1S.. If S is small, such es normallyoccurs in cables, the increase in D" will be small and no distortion ofthe strand will result.

In this analysis, we have assumed d constant. For some constructionsthis might not be justified but for the usual constructions and for Sless than 1/6 the change in d is negligible.

It will be seen from all of the foregoing that the present inventionprovides an electric cable construction in which the conductor isapplied about an incompressible but extensible core with such a laywhich I have termed a critical lay, that the inside diameter of thehelix provided by the conductor initially contracts or decreases justslightly faster than the outside diameter oi the core so as to controlor restrict to a predetermined extent the elongation of the conductorwith a given predetermined elongation of the cable, this stretch of theconductor, however, is

' not sufiicient to prevent the conductor contract" ing without bucklingas the cable contracts, the conductor remaining out of contactthereafter with the core except on subsequent elongations of the cablewherein at the limit of elongation for which the cable is designed theconductor again is drawn into contact with the core. In

' other Words, the lay is such that the inside diameter of the helixprovided by the core always decreases faster than the outside diameterof the core, the initial elongation of the cable causing the conductorto stretch permanently so that on subsequent elongations the conductorwill elongate without stretching until it contacts with the surface ofthe core.

Various types of conductor may be employed in the practice of myinvention and in Figs. 8, 9 and 10 I have illustrated types of conductordiierent from that shown in Fig. 1, 8a showing a conductor made up of agroup of strands previously twisted together, 9b a tape and IIIe wovenor braided tape.

The invention of this application may be embodied in multi-conductorcables.

In Fig. 11 I have illustrated a multi-conductor cable in which aplurality of single conductor cables of the same type as shown in Figs.1 and 2 are assembled around a 'core of hemp or other suitable material,these cables being designated I and the core II.

In Fig. 12 I have illustrated another modification in which two cablesI2 of the type shown in Flg. 2, for instance, but Without the supportingarmor wire, are twisted together, a circular cross section built up withjute I3 surrounded by tape I0, and a. plurality of single conductorcables I of the type shown in Figs. 2 or 11 laid about this assembly.

What I claim is:-

l. An electric cable comprising in combination a core of extensible,substantially incompressible material, and a conductor helically appliedabout and in contact with said core with such a lay that initially werethe cable compressed longitudinally the core would increase in diameterfaster than the conductor, While on elongation the conductor would tendtoy pull down on the core.

2. n. multi-conductor cable comprising in combination a plurality ofsingle conductor cables twisted together and each composed of a core ofextensible substantially incompressible material, a conductor helicallyapplied about and in Contact With said core with suon a lay thatinitially were the cable compressed longitudinally the core wouldincrease in diameter faster than the conductor, while on elongation theconductor would tend to pull down on the core, a plurality of similarsingle conductor cables laid up about said first mentioned cables, eacho the last mentioned cables being enclosed in supporting Wires.

3. A multi-conductor cable comprising in combination a plurality ofsingle conductor cables disposed about a central core, each singleconductor cable comprising a core of extensible, substantiallyincompressible material, a kconductor helically applied about and incontact with said core with such a lay that initially were the cablecompressed longitudinally the core would increase in diameter fasterthan the conductor, while on elongation the conductor would tend to pulldown on the core, and armor supporting wire for each cable.

4. An. electric `cable comprising in combination a core of extensible,substantially incompressible material, and a conductor helically appliedabout and in contact with said core with such a lay that initially werethe cable compressed longitudinally the core would increase in diameterfaster than the conductor, while on elongation the conductor would tendto pull down on the core, insulation about the conductor and supportingwires about said insulation.

RICHARD C. WALDRON.

